B5- Homeostasis Flashcards
What is kept the same in the human body?
- Water levels.
- Temperature.
- Glucose levels.
- Salt levels.
What is a stimulus?
A change in external environment.
What is a reflex?
An automatic and instantaneous nervous response which does not require conscious thought and helps prevent injury.
What is the name given to the part of the nervous system which contains only nerves?
The peripheral nervous system.
What is the hormone system called and what does it do?
The endocrine system - sends hormones around the body through the blood.
What are hormones produced by?
Endocrine glands.
What are hormones? (3 points)
Chemical messengers which control things that need constant adjustment in organs and cells. They have long lasting effects and act in a general way.
Why is homeostasis important for the body?
Cells need the right conditions to function properly, e.g. enzyme action.
What is negative feedback?
Receptors detect stimuli, like levels of a hormone being to high. The coordination centre organises a response and the effector produces a response which counteracts the change. The optimum level is restored.
Where is the pituitary gland?
At the base of the brain.
Where is the thyroid?
Along the front of the windpipe.
Where are the ovaries?
In the lower abdomen.
Where are the adrenal glands?
One above each kidney.
Where are the testes?
In the scrotum.
Where is the pancreas?
Behind the stomach.
What is the role of the pituitary gland?
Produces many hormones which regulate body conditions. Some of these hormones act on other glands, which produce other hormones.
What is the role of the thyroid?
Produces thyroxine, which regulates things like rate of metabolism, heart rate and temperature.
The pituitary gland produces TSH (thyroid-stimulating hormone), which regulates production of these hormones.
What is the role of the adrenal glands?
Produce adrenaline in stressful/scary situations, to prepare for a fight or flight response.
What is the function of adrenaline?
Triggers mechanisms which increase the supply of oxygen and glucose to cells in the brain and muscles, to prepare for a fight or flight response. E.g. triggers an increased heart rate.
What is the role of the pancreas?
Monitors and control blood glucose levels: produces insulin and glucagon. Also produces enzymes.
How does a nervous response compare to an endocrine one?
Nervous: faster, short-lasting action on a precise area. Endocrine: slower, longer lasting response on a general area.
What are the food groups?
Carbohydrates, lipids and proteins.
What are lipids made of?
Glycerol and fatty acids.
What are the types of carbohydrates and what are they all made of?
All made of strings of glucose molecules:
In plants: fibre, starch, cellulose.
Animals: glycogen.
What are amino acids made of?
Glucose and nitrate.
What happens when blood glucose levels are too high?
Insulin is secreted by the pancreas and is carried by the blood to the liver. Here, the insulin triggers the liver to turn excess glucose into glycogen, which is stored in the liver and muscle cells.
What happens when blood glucose levels are too low?
Glucagon is secreted by the pancreas and is carried by the blood to the liver. Glucagon triggers the liver to convert stored glycogen into glucose, which is released back into the blood.
What is type 1 diabetes?
The pancreas produces little or no insulin, so glucose can rise to dangerous levels.
How is type 1 diabetes controlled and treated?
1) Regulation of simple carbohydrate consumption and regular exercise. 2) Insulin therapy used, involving several insulin injections per day, usually at mealtimes, to stop sugar levels getting too high. The amount of insulin needed depends on diet and activity.
What is type 2 diabetes?
Although insulin is produced, body cells don’t respond properly to, and become resistant to, the body’s own insulin. Causes blood glucose levels to rise dangerously.
How can type 2 diabetes be controlled?
Regulation of simple carbohydrate consumption and regular exercise.
If not enough, then tablets and sometimes even insulin.
What is the role of thyroxine?
Regulates basal metabolic rate, heart rate and temperature. Also stimulates protein synthesis for growth and development.
What stimulates thyroxine to be produced?
TSH.
What is thyroxine made of?
Iodine and amino acids.
What is the function of the cerebral cortex?
Responsible for consciousness, intelligence, memory and language.
What is the function of the medulla?
Controls unconscious activities, e.g. breathing and heartbeat.
What is the function of the cerebellum?
Responsible for muscle coordination and balance.
Why is it difficult to: 1) investigate brain function? 2) treat brain damage/disease?
The brain is very complex and delicate. 1) Many processes involve neurones in different areas. 2) Treatment carries risks such as physical damage to the brain, or functional problems, e.g. speech impairment.
What is the sclera?
The tough white outer layer of the eye.
What is the cornea?
The transparent outer layer at the front of the eye which refracts light.
What is the iris’ function?
Controls the diameter of the pupil, and therefore how much light enters the eye, so that there is enough to stimulate, but not damage, the cones.
What is the function of the lens?
Focuses and fine-tunes light onto the retina.
What is the function of the ciliary muscles and suspensory ligaments?
Alter the shape of the lens.
What is the function of the optic nerve?
Carries images from receptors, on the retina, to the brain.
How have neuroscientists studied people with brain damage to better understand the brain?
Matching changes in behavior/memory with a damaged area of the brain has helped scientists to map the functions of certain areas.
How do neuroscientists use electrical stimulation to investigate brain function?
By inserting an electrode into brain tissue, they can observe the effects of stimulating certain areas, and map their functions.
How do neuroscientists use MRI scanners to investigate brain function?
These produce a detailed image of the brain, showing which areas are active when people are thinking certain things. This helps map the functions of certain areas.
(Like other types of scanners, they show the brain’s anatomy well, so can be used to map areas of damage to their function.)
How does the eye respond to bright light?
1) Light receptors detect bright light. 2) Circular muscles in iris contract 3) Radial muscles relax. 4) Makes pupil smaller, reducing amount of light entering eye. 5) Protects retina. =iris reflex
How does the eye respond to dim light?
1) Light receptors detect dim light. 2) Circular muscles in iris relax. 3) Radial muscles contract. 4) Makes pupil larger, increasing amount of light entering eye. 5) Lets more light in so can see well =iris reflex
What is accommodation?
The ability of the eye to alter its focus between near and distant objects.
How does the eye accommodate to focus on near objects?
1) Ciliary muscles contract.
2) So suspensory ligaments slacken.
3) Lens becomes more convex (fat).
4) Increases amount by which it refracts light.
How does the eye accommodate to focus on distant objects?
1) Ciliary muscles relax.
2) So suspensory ligaments tighten.
3) Lens becomes less convex (less fat).
4) Decreases amount by which it refracts light.
What is hyperopia?
Long-sightedness: inability to focus on near objects.
What is myopia?
Short-sightedness: inability to focus on distant objects.
Explain the cause of hyperopia.
1) Lens isn’t convex enough, so doesn’t refract light enough / eyeball is too shallow. 2) Images of close objects are focused behind the retina.
How can hyperopia be corrected?
Wearing glasses with a convex lens (curves outwards) which refracts light to focus on the retina.